Security researcher says flaw has major implications for virtual keyboards

A vulnerability affecting Internet Explorer versions 6 through 10 could make it possible for a hacker to monitor the movements of your mouse, even if the browser window is minimized.

According to U.K.-based Web analytics firm Spider.io, this means that passwords and PINs could be captured by a canny thief if they are typed on an onscreen keyboard. What's more, it's already being exploited by two display advertising networks, the company said, though it did not name them.

"As long as the page with the exploitative advertiser's ad stays open -- even if you push the page to a background tab or, indeed, even if you minimize Internet Explorer -- your mouse cursor can be tracked across your entire display," Spider.io said. The company added that, while the problem has been acknowledged by the Microsoft Security Research Center, there are apparently no immediate plans for a patch.

Spider.io also published the technical details of the exploit, which involves the browser's global Event object, as well as a game demonstrating how it could be used to monitor user input to a virtual keyboard. "Internet Explorer's event model populates the global Event object with some attributes relating to mouse events, even in situations where it should not. Combined with the ability to trigger events manually using the fireEvent() method, this allows JavaScript in any Web page (or in any iframe within any Web page) to poll for the position of the mouse cursor anywhere on the screen and at any time," the company said.

Email Jon Gold at jgold@nww.com and follow him on Twitter at @NWWJonGold.